The Second Half of Life: Skyview Acres Star Party

With my son, I attended the Skyview Acres star party June 11-12 near Goldendale, WA. This was the first time I've used the new RV for this purpose and it sure does make things better! Being able to go inside and warm up in front of a furnace vent is such a pleasure. In this case though, the cold wasn't so bad... it was the dew.

With temperatures in the mid-40's I was hopeful that I could start my imaging season as early as May, based upon the weather history. Last year I started late enough that I never encountered any dew. This year I've imaged twice and both times there was more moisture in the air than any time last year (when I started in August after finally getting all of the necessary equipment). In May, in my backyard, I took an image of M101 and saw some strange artifacts in the background. I suspected dew or frosting in my camera and replaced the desiccant bag in the CCD chamber just before this trip. It didn't work.

My primary suspect now is either condensation on my objective lens or inside the camera on the cover plate to the CCD chamber. There was no evidence of a cleanliness issue on that plate or the filters when I replaced the desiccant bag. Next time I image it needs to be in dry conditions to test this theory.

The Skyview Acres site was bad for dew because there was a lot of fairly tall grass and moisture in the ground. That moisture became worrisome early in the evening when it started condensing out on my table. I never really saw or felt any on my telescope, but I can't rule out that it was there in very small droplets. Conditions were certainly on the edge.

I went ahead with my imaging both nights but quit in the range of 1am to 2am, primarily because of the dew concerns. On the second night I had thought the dew situation would improve. It had been warmer during the day and a bit warmer at night, but the dew actually seemed worse.

The first night I imaged two objects (M63 and M100) in black and white only. Early on it became evident that my camera was not working right and I diagnosed that it wasn't taking dark images properly. Instead, they were similar to the light images and when they got subtracted off with slight motion of the scope (unguided) it left "shadows" beside all of the stars. I got around this the first night by taking a set of manual darks (covering the lens with the cap) and taking light images only. The next day I took apart my camera and found that I had not properly set the color filter wheel in place on its axle and it had come loose.

M63 and M100 were targets because I had never seen them before (weren't in the sky when I started last year) and they seemed to be interesting objects (not just fuzzy blobs). M100 is a pretty spiral galaxy and M63 is a galaxy with an odd dark arc around one side of its core, earning it the name "The Black Eye" galaxy. These were both smaller and fainter objects than I've typically imaged in the past. M64 is 10'x5' in size and magnitude 9.3. M100 is 7.6'x6.8' in size and 10.0 magnitude. I used no auto-guiding that night, so I was confined to getting multiple short (1 min) exposures that I would later stack together. The resulting pictures are shown below, where, for M100, I included a pre-processing image and a post-processing image, to give you an idea of just how much clean-up happens even after the darks are subtracted and the images were stacked. Total exposure time on M100 was 21 minutes and on M64 was 11 minutes. You can easily see the "black eye" feature, but little else on M64. M100 could have used more exposure time, but it's really nice spiral shape is very evident... it's just really small! Objects of this size could really benefit from using a longer focal length scope for imaging.

The second night I imaged three objects: M101 (spiral galaxy, 21.9'x21.4, mag 8.4), M5 (globular cluster, 23'x23', mag 5.7) and M8 (The Lagoon Nebula, 17'x15', mag 5.0), in that order. You can see that the sizes of these were around 2x or more larger and they were all brighter than M64 and M100. Images, post processing are shown below. M101 needs more processing work but may be too limited by the artifacts for the color image to ever be all that good. Both color images are LRGB, combining Red-Green-Blue filtered images with an image taken without any filter (Clear). This is the first time I've created such images successfully, having utilized Photoshop and instructions from Ron Wodaski's first book. In order to get the color to come out right, I had to pretend that the Blue filter (Blue based upon appearance) was Red and vice-a-versa... something I still need to explain. When I had the camera apart, I tested the filter wheel and noted that what was specified by the software was not what the ST-402 camera delivered. Instead, "Blue" was clear, "Clear" was green, "Red" was blue, and "Green" was red. I thought I may have gotten the filter wheel on in the wrong position, so I changed it 180 degrees and the got the same result. If my error is judging the filter by its naked eye appearance, that still can't explain why specifying "Blue" results in no filter in front of the CCD. An email to SBIG is warranted.

All in all, this was a good trip. The M8 photo was pretty good and I again learned a lot about what can go wrong. Hopefully future sessions will be better because of it.